A recent blast from a dying star has left astronomers, gaping in awe at the sheer magnitude. A distant eruption, classified now as a Gamma Ray Burst (GRB) and named GRB 130427A, has now set the record for the brightest GRB ever. NASA’s Swift satellite and Fermi-LAT, both specialized for the gamma ray part of the spectrum, have recorded this mind-boggling event. Julie McEnery, project scientist for NASA’s Fermi-LAT, said that this was a “shockingly, eye-wateringly bright” burst.

An artist’s impression of a GRB. Note the strong jets on either side of the collapsing star. (Courtesy: wikimedia commons)

What are GRBs?

Gamma Ray Bursts are the most powerful explosions known to mankind that occur in the Universe, ranked second right after the Big Bang itself. GRBs occur when an extremely massive star collapses into a massive black hole, and the material falling into the black hole heats up so much that it radiates in the gamma ray region of the spectrum. These jets of gamma rays puncture the material envelope of the dying star and can be detected from a long distance. Unlike smaller supernova (which happen for moderately large stars), GRBs are responsible for throwing out a large amount of energy in the surrounding space, often energizing the gas around and making it glow. The duration for such a burst might last from a few milliseconds to minutes or even hours and the burning embers can often be seen for days and months. We generally count the time for which the radiation energy exceeds the GeV (giga-electron volt) threshold, which is about a billion times more energetic than visible light.

Our GRB

For our present GRB, the GeV radiation lasted for hours and it was observed by Fermi-LAT, a space based gamma ray telescope, for a long time. Even ground based telescopes caught more than a glimpse of the GRB. The Swift satellite caught the first glimpse, as it is designated to do, during one of its rounds. Energetic emissions were recorded by Fermi-LAT, with one of the gamma ray lines having an energy of 94 GeV.

This animation is made by stacking a large number of images taken by the Fermi-LAT satellite from 3 minutes before the burst to 14 hours later. You can clearly see the burst and then the radiation flux drops and plateaus off. The burst then rose in flux again and stayed bright (GeV energy lines were abundant) over several hours. (Courtesy: NASA/DOE/Fermi-LAT collaboration)

Apart from the strong gamma emission lines in the spectrum, there are also lines present in the infrared, visible and radio wavelengths. These were detected by ground-based telescopes. The distance of the burst was estimated to be 3.6 billion light years away, which is actually quite small when it comes to GRBs. This falls within the 5% of the closest GRBs ever recorded.

This is exciting and a lot of backup measurements will follow this initial detection.

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.

Debjyoti Bardhan has written
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